1. Field of the Invention
The present invention relates to optics. More specifically, the present invention discloses a miniaturized linear light source sub-module comprising a highly efficient light guide with a first reflecting surface to maximize light reflection and a second reflecting surface to enhance the uniformity of the emitted light, at least one light emitting diode light source, an array of lenses for high-resolution imaging of a surface, and a sub-module housing.
2. Description of the Prior Art
Linear light sources emit light in a different direction from the direction the light originated from. For example, a light is produced by a light emitting diode at an angle of zero degrees. By affecting the direction of the light beam the linear light source can emit the light at various angles such as 90 degrees.
Refer to FIG. 1A, which is a drawing illustrating a light source of the prior art. As shown in FIG. 1A, the conventional light source comprises a light emitting diode 110 and a transparent light rod 120. Both ends of the transparent light rod 120 are flat surfaces. When power is applied to the light emitting diode 110 the light emitting diode 110 emits light. Some of the light enters the transparent light rod 120. However, since the end of the transparent light rod 120 is flat, much of the light is reflected back and is lost. This lowers the efficiency and intensity of the light source.
The light that enters the transparent light rod 120 exits the side surface of the transparent light rod 120. Unfortunately, some of the light exits the transparent light rod 120 in directions not intended. This results in an additional loss of light. To overcome this disadvantage a reflective housing must be used in order to try to reflect the escaping light back into the transparent light rod 120. This increases the cost of the light source.
Additionally, since only one light emitting diode 110 is utilized in the conventional light source the emitted light is brighter closer to the light emitting diode 110 and dimmer at the far end of the transparent light rod 120. As a result the conventional light source's emitted light is not uniform.
Therefore, there is need for an improved light guide for a linear light source that is highly efficient and provides an emitted light that is uniform in intensity.
Traditionally, the lens for a one to one imaging optical scanner is a rod lens array. Please refer to FIG. 1B, a perspective drawing of a prior-art rod lens array 130. The rod lens array 130 is constructed from a plurality of fiber optic rod lenses 131. Each individual fiber optic rod lens 131 is cut from a fiber optic glass strand, and its ends must be polished. The plurality of fiber optic rod lenses 131 are then arranged side by side, in a row or multiple rows with their optical axes in parallel, in a frame 132 and held in place by an adhesive layer 133. The fiber optic rod lenses 131 are typically made from GRIN (graduated index) fibers, with the refractive index of the glass carefully controlled during manufacture to have a graduated refractive index that decreases radially from the central axis to the edge.
However, this type of lens is expensive to manufacture. GRIN type fiber optic glass strands are expensive in and of themselves; cutting and polishing the strands to precise lengths to form fiber optic rod lenses 131, assembling them so that their axes are precisely parallel in the frame 132, and gluing the fiber optic rod lenses 131 are all precision steps for which entire technologies have had to be developed in order to satisfy requirements.
In addition, a major disadvantage of this type of lens is that because of the number of lenses and the difficulty in orienting them, it is not practical to shape the ends of the lenses so that they can magnify the surface that they are imaging; flat ends are used. In order to increase the imaging resolution, it is necessary to use larger numbers of smaller-diameter rod lenses 131, limiting the maximum resolution and driving up the costs as the desired resolution increases. Furthermore, suppliers for the necessary GRIN fiber optic strands are limited, and thus the base materials themselves are expensive.
Additional, the glass used in the conventional rod lens contains lead which is not environmentally friendly.
Therefore there is need for an improved lens array for which materials are substantially cheaper and which is simpler to manufacture, and which can have increased resolution without substantially increasing costs.